1. Field of the Invention
The present invention relates to a cap for a recording head used for sealing tightly an ink ejection orifice of an ink jet recording head so as to protect the orifice, and an ink jet recording head in which the cap for a recording head can be mounted.
2. Description of the Related Art
One of the most important factors which determine the reliability in recording information by ink jet recording heads is a physical condition around the ink ejection orifice (hereinafter referred to as "orifice" simply) and a physical condition of ink fluid to be ejected outside the orifice. More specifically, extraneous substances such as dust and liquid drops on and around the orifice may deflect an ink drop let being ejected, and an increase in viscosity of ink in a liquid path near the orifice may lead an ink ejection to be faulty condition such as non-ejection. An attachment of such unfavorable extraneous substances and such increase in viscosity of ink fluid occur when the orifice of the recording head is exposed to the atmospheric air, for example, during ejecting ink for recording information or waiting for recording operation. It is known that, in order to prevent the attachment of such unfavorable extraneous substances and such increase in viscosity of ink, the orifice is capped with an adequate device except when the orifice is used for recording operation or the like, or the surface on which the orifice is disposed is wiped with a blade and so on according to demand.
It is easier to remove unfavorable extraneous substances by way of the above mentioned devices in case that the recording head is installed in the recording apparatus. However, in case that the recording head is shipped and transported from the factory to users through temporary storages, it may be required that some preventive method for removing unfavorable extraneous substances on the recording head and for reducing an increase of the viscosity of ink fluid should be employed.
Especially in case of exchangeable recording heads which can be installed in and removed from the apparatus body freely, as storage and transportation of such exchangeable recording heads are directed to an individual recording head separated from the recording apparatus, the above mentioned device for capping the recording head installed in the recording head cannot be directly applicable.
In addition to the above mentioned problems in removing unfavorable extraneous substances and preventing an increase in the viscosity of ink fluid, it is required to prevent ink fluid leakage due to external force and shock while transporting the recording head and due to a temperature change outside the recording head. In order to solve these problems, in some prior art apparatus, employed is a cap the structure of which is different from that used in the apparatus when installed. An example of such a cap is shown below.
As shown in FIG. 1, in Japanese Patent Application Laying-open No. 37436/1986, disclosed is a structure where a cap 70 covers the whole surface on which orifices 71a of the recording head 71 are arranged so that a swelling material inside the cap 70 absorbs ink fluid from the orifices 71a and swells so as to seal the orifices 71a. Alternatively, FIGS. 2A, 2B and 2C also show a structure where a seal 80 is bonded on the surface on which orifices 81a of the recording head 81 are arranged so that the orifices 81a are sealed.
And furthermore, with a combination of a seal 90c and a pressing member 90b as shown in FIGS. 3A and 3B, by the assignee, proposed is a structure 90 where the seal 90c is pressed against the face 91a on which an orifice 91e of the recording head 91 is disposed. The structure is disclosed in WO/91/08267.
In this structure, the seal 90c which is larger than the orifice disposed face 91a is bonded onto the orifice disposed face 91a by using bonding materials with relatively weaker adhesive property. The bonded seal 90c is pressed by the pressing member 90b with a designated amount of force developed on the face around the orifices 91e on the orifice disposed face 91a. As a result, the orifices 91e are shielded completely against the atmospheric air and evaporation of ink fluid from the orifices 91e is prevented. A pressing force developed by the pressing member 90b is applied by means that a couple of arms of the cap 90a is caught by a part of the recording head 91 when the cap 90a is installed in the recording head 91.
Bonding materials used for contacting the seal 90c and the orifice disposed face 91a have a weak adhesive property as described above. That is, there is no need to guarantee complete sealing of the orifices by bonding the seal 90c itself, and hence, the seal 90c may have an adequate adhesive property so as to establish contacting of the seal 90c on the orifice disposed face. So far, it will be appreciated that the amount of bonding materials can be limited to be small enough to establish contacting of the seal 90c on the orifice disposed face and that unfavorable penetration of excess bonding materials into the orifices can be avoided so that bonding materials may not give unfavorable effect on ink ejection operations.
In the above mentioned structures for capping the recording head, the following problems still remain to be unsolved. In the structure using the cap 70 shown in FIG. 1, though ink fluid leakage is prevented even when external force and shock are applied or excess amount of temperature changes occur, there may be a case that leaked ink fluid from the orifices 71a is staying in a space between the swelling material in the space 71b and the cap 70. In this case, for example, when the cap 70 is removed in order to install the recording head in the recording apparatus by the user, ink fluid remained in the space may flow over the cap 70 and may be spattered over hands of the user, and even may lead to electric parts failure due to spilled ink fluid in the recording apparatus.
In the structure using the seal 80 as shown in FIGS. 2A-2C, it may not be easy to install the seal 80 on and around the orifices of the recording head precisely. When removing the seal 80 installed on the orifice disposed face, strong bonding materials used for contacting the seal 80 may be still present on the face near the orifices so that ink fluid ejection failure may be brought. On the other hand, when bonding materials with weak adhesive property is used, the seal of the recording head by the seal 80 is not completely established. And in case that the surface of the orifices is not continuously formed on its neighboring area, the seal 80 cannot seal the surface and its neighboring area completely.
Even in the structure as shown in FIGS. 3A-3C, in case that the surface 91a of the orifices 91 is not continuously formed on its neighboring area and the surface 91a is concave on the neighboring area, it may not be easy to bring the seal 90c into close contact with the orifices 91e by the pressing member 90b. These contact failure leads to incomplete seal to the orifices.
For example, in case that the orifice disposed face to be shown in FIG. 8 of the present invention where a cross-sectional shape of the orifice disposed face is a concave (arc) shape and the orifices is not placed in the bottom of the concave shape, the distribution of pressing force developed by the pressing member is not uniform over the concave shape because the shape of the contacting face of the pressing member 90b is a flat plane. That is, there may be a case that pressing member 90b cannot be deformed in responsive to the curved shape of the orifice disposed face and that, as a result, a well-conditioned contact between the seal 90c and the orifices 91e cannot be established.
In addition, in the structure shown in FIGS. 3A-3C, the pressing member 90b is composed of elastic and porous materials such as silicon porous materials and polyurethane porous materials which have a thickness of about three millimeters. In this case, as the pressing member 90b has about 50 cells of air voids per 1 inch, seven to eight orifices may be defined in the corresponding cell. These orifices contacting cells of air voids are not pressed directly by the substantial pressing member 90b through the seal 90c, and these orifices are pressed only by the seal 90c. As a result, which leads to unfavorable phenomena such as an increase in the viscosity of ink fluid absorbed in the pressing member 90b and spilt ink fluid around the orifices.
Furthermore, in the above mentioned structure of sealing and capping the recording head, there may be a problem that the number of additive components for sealing and capping the recording head inevitably increases.